timer for furnace blower

timer for furnace blower

PostBy: sakrattack On: Wed Dec 16, 2009 12:44 am

question--i have a heat jacket tied into return side of forced air duct....instead of using a fan limit switch that would turn on/off the furnace blower according to a certain temp/s,,,could i simply use a timer that would turn off and on the furnace blower?--meaning would the col-trol after a certain amount of time "learn" and adjust stove and have the same outcome as the fan limit? for instance 15 min off, then on for 5, etc, etc...(put in any number you want)... would the col trol know after a day or so and the house be able to maint the set temp?
thank you much
sakrattack
 

Re: timer for furnace blower

PostBy: pvolcko On: Wed Dec 16, 2009 3:56 pm

I'm not sure I understand what you're asking.

The Coal-trol will run the stoker at the rate needed to maintain the setpoint. The furnace fan limit switch will control when the blower turns on and off based on the temp of the air in the plenum or rear air channel of the stove (depending on where you have the switch installed). The Coal-trol doesn't know about the independent fan control or what it is doing from moment to moment, but it will do its best to adjust the stoker to meet the temperature setpoint regardless of the behavior of the fan limit switch. In some cases the fan limit switch (particularly if it is set to a high "on" temperature and a relatively low "off" temperature) can result in an unstable temperature in the house. Ideally the fan switch will come on at a low to moderate temp and the off temperature will be near your average room temp. Also, you may want to leave one of the convection fans installed and hooked up to the coal-trol so it can help push the stove's heated air to the furnace fan limit switch, particularly if the limit switch is installed after a horizontal run of duct instead of in the stove's air channel or directly above it. This will help couple the coal stove output to the furnace fan and result in a smoother temperature response in the house.

If I'm not hitting on the thrust of your question, please give it another try. I'll catch on eventually. :)
pvolcko
 

Re: timer for furnace blower

PostBy: sakrattack On: Wed Dec 16, 2009 5:31 pm

thanks,,,perhaps your last sentence hits upon the answer ie the smoother temp response in the house,,, but let me try again though....lets say i simply put a timer on my furnace blower,,,so it turns on and runs for 5 minutes, then turns off for 15-20 min....after a day or so would that method accomplish the same thing as the fan/limit method? i completely understand the fan limit way,,,i am just wondering if the timer method would work as well..
my first thought is that the blower would blow cool air but if the coal trol is working then it wouldnt. again, i may be completely wrong in my thinking. using the fan limit way might be the best way to go...i was just wondering running the furnace blower at set intervals would accomplish the same thing..
thank you again
sakrattack
 

Re: timer for furnace blower

PostBy: Sting On: Wed Dec 16, 2009 5:36 pm

a house stat like this

http://www.luxproducts.com/thermostats/cag1500.htm
This link is broken, either the page no longer exists or there is some other issue like a typo.

can be programed to stir that cold air back out of the corners and help even the temp in the house on these cold nights -
Sting
 
Other Heating: OBSO Lennox Pulse "Air Scorcher" burning NG

Re: timer for furnace blower

PostBy: pvolcko On: Wed Dec 16, 2009 7:45 pm

sakrattack,

We recommend against changing from a limit switch to a timer for furnace fan control purposes. While the 5/15 timing setting might work for certain feedrates from the coal-trol, it almost certainly would not work across all feedrates. Particularly, at higher feedrates the BTUs produced may well require longer run times than your timer is set to. This would result in both poor distribution of heat into the home (and thus poor temperature control and fuel efficiency from the Coal-trol) and it may well cause the furnace fan to become overheated as abnormally hot air is put through it in the too-short 5 minute run time.

That said, if you are wanting to have the furnace fan turned on for "stirring" purposes, you could wire a line voltage timer in parallel with the limit switch so that both can activate the furnace fan. That way high BTU output conditions will run the fan when needed and longer than the timer's settings, and in low BTU output situations the timer will provide a minimum "stir" timing.

If you are experiencing issues with cold corners that running the fan helps, you could always run the fan continuously, too.

This stir mode that Sting brings up is an interesting feature idea. Will put it on the wish list for future versions.
pvolcko
 

Re: timer for furnace blower

PostBy: 009to090 On: Wed Dec 16, 2009 8:48 pm

We run our Carrier furnace fan continuously, but it is variable speed, and set for 20% output while we are heating with solid fuel. No special timers or switches needed.
009to090
 
Stoker Coal Boiler: EFM 520 HighBoy
Hot Air Coal Stoker Stove: DVC-500 x 2
Coal Size/Type: Anthracite Rice

Re: timer for furnace blower

PostBy: sakrattack On: Thu Dec 17, 2009 11:39 am

excellent now i understand. thanks so much,,good explanation
sakrattack
 

Re: timer for furnace blower

PostBy: McGiever On: Wed Dec 22, 2010 12:00 am

Sting wrote:a house stat like this

http://www.luxproducts.com/thermostats/cag1500.htm
This link is broken, either the page no longer exists or there is some other issue like a typo.

can be programed to stir that cold air back out of the corners and help even the temp in the house on these cold nights -


Revised link:


http://www.luxproducts.com/thermostats/cag1500.php
This link is broken, either the page no longer exists or there is some other issue like a typo.
McGiever
 
Stoker Coal Boiler: AXEMAN-ANDERSON 130 "1959"
Hot Air Coal Stoker Stove: HARMAN MAGNUM
Hand Fed Coal Stove: RADIANT HOME AIR BLAST
Baseburners & Antiques: OUR GLENWOOD 111 BASEBURNER "1908"
Coal Size/Type: PEA / ANTHRACITE, NUT-STOVE / ANTHRACITE
Other Heating: Ground Source Heat Pump
Stove/Furnace Make: Hydro Heat /Mega Tek

Re: timer for furnace blower

PostBy: AA130FIREMAN On: Wed Dec 22, 2010 12:12 am

I have an aquastat in my forced air duct, I keep the fan on run (so it would run all the time) and use an aquastat to sence the temperature, if it's hot it makes and the electric starts the fan, aquastat breaks the circut on temperature drop, stopping the electric to the fan.
AA130FIREMAN
 
Stove/Furnace Make: axeman anderson
Stove/Furnace Model: 130 anthratube